Charge retention

Ruggedness

Good points

But

How we test

We place the batteries in a computer-controlled test rig that charges them, then discharges them at a rate equivalent to the demand of a high-drain device — like a remote-controlled car. Once the cell voltage reaches 1.0V, equivalent to empty for most power-hungry devices, the rig charges them again.

We judge each battery’s long term endurance by measuring how many cycles until its capacity falls to half its initial value.

The battery’s average capacity over the amount of charge/discharge cycles before failure gives our battery life per use score.

Rechargeable batteries gradually lose charge while sitting idle. We measured this rate of “self-discharge” for each battery to get our charge retention in storage score.

We also look at the ruggedness of each battery’s construction by placing them in a rotating cylinder (a bit like a gentle tumble-dryer) for 24 hours, before taking them out and sorting them from least to most damaged.